Update for 500MB file uploads and enhance Entra ID setup instructions

pdf_renamer.py

@@ -11,7 +11,7 @@ from authlib.integrations.flask_client import OAuth
 
 app = Flask(__name__)
 app.config['UPLOAD_FOLDER'] = tempfile.mkdtemp()
-app.config['MAX_CONTENT_LENGTH'] = 100 * 1024 * 1024  # 100MB limit
+app.config['MAX_CONTENT_LENGTH'] = 500 * 1024 * 1024  # 500MB limit
 app.secret_key = os.getenv('SECRET_KEY', 'dev-secret-key-change-in-production')
 
 # Entra ID Configuration